True VTC noise can be verified by activating the VTC solenoids using a ConZult or by grounding their green with black stripe wires while the engine is idling. This will cause oil pressure to build within the pulley, forcing the VTC piston to screw onto the VTC helix thus advancing the cam and removing the window of opportunity to make noise. Typical VTC noise will stop entirely when doing this and the engine will begin to idle rough due to increased valve overlap.
